When appropriately indicated, modern medical treatment frequently includes the procedure of moving fluid from one location in the body to another or between the body and an external apparatus. In a ventriculoperitoneal (VP) shunt for treating hydrocephalus, among other conditions, cerebrospinal fluid (CSF) is transferred from a ventricle of the brain to a receiving reservoir, such as the heart or peritoneum. A basic VP shunt system typically includes a proximal cannula for draining fluid from the ventricle, a subcutaneously implanted pressure valve connected to the proximal cannula, and a distal cannula connected subcutaneously between the pressure valve and the reservoir. The shunt may include other instruments, such as a flushing device and an injection port for administration of medicine or extraction of fluid samples.
Generally shunts employ thin walled, small diameter rubber tubes to conduct fluid throughout the shunt system. A common technique for joining two tubes together or for joining a cannula to an instrument uses a connector fitting with a tubular, cylindrical nipple. The nipple has a larger outer diameter than the inner diameter of the tube being joined. Inserting the nipple into the lumen of the tube stretches the tube walls, and produces a radially compressive force which forms a liquid tight seal between the tube and the nipple due to the elasticity of the tube.
It is extremely important that the tube does not disconnect from the nipple unexpectedly. For a subcutaneously implanted tube, accidental tube disconnection is particularly undesirable because surgical procedures are needed to make repairs. Although tube wall stretching provides some resistance against the tube disconnecting from the nipple, surgeons customarily tie one or more circumferential ligatures of suture thread around the tube at each nipple to increase resistance. However, if the ligature is too tight, the thread can cut through the tube wall, and in time, partially or completely sever the tube. In tying the ligature too tightly, the physician can also move the instrument out of position which sometimes causes the shunt to malfunction. If the ligature is too loose, it will not help to keep the tube on the nipple. Because ligatures are tied manually, whether or not the ligature tension is proper depends a great deal on the skill and dexterity of each treating physician.
VP shunt connection ligatures are more difficult to tie properly when the incision is small and the connection is partially hidden under the skin. This commonly happens when a previously implanted shunt is repaired. In order to remove an old knot and tie a new one, the physician usually enlarges the incision to provide adequate access. Large incisions take longer to heal, cause more discomfort and generally disfigure more than small incisions. Therefore, physicians must sometimes make incisions larger than desirable in order to manually ligate a tube connection.
Subcutaneous tube connections secured by ligatures also present the disadvantage that scar tissue tends to grow around the ligature. Scar tissue growth can anchor the tube-to-nipple joint to the body, which restricts free movement of the instrument within the patient. As the patient grows, the instrument can be pulled out of position or the tube can break or pinch. Excessive scar growth around the ligature also often makes it difficult to surgically revise a shunt.
In another aspect, the present invention relates to the medical tube connector material of construction. Conventional subcutaneous VP shunt connectors are made of stainless steel or nonmetallic materials, such as polymers. Although adequate for fluid transfer purposes, nonmetallic materials are not radioopaque. Consequently, it is difficult to verify position of the connectors subsequent to implantation. Stainless steel connectors are radioopaque, but they can distort magnetic resonance images (MRI). MRI scanning is an increasingly popular tool for noninvasive, internal soft tissue evaluation.
Another aspect of the present invention relates primarily to a proximal cannula of a VP shunt. The proximal cannula is usually a tube with a right angle elbow bend between the ends to form two arms. One arm of the tube is inserted into a ventricle of the brain through a hole drilled in the skull for this purpose. The second arm is placed outside and adjacent the skull for connection to a subcutaneously implanted shunt pressure valve. A conventional proximal cannula is made by bending a normally straight, flexible tube. Due to the rubbery nature of the tube, the inserted arm tends to return to a straight orientation causing the arm to withdraw from the ventricle or pinch against the rim of the hole. If the physician overbends the tube, i.e., to an acute angle, the tube can kink and occlude. Sometimes a right angle clip such as is available from Pudenz-Shulte Medical, Goleta, Calif., is mounted on the tube to impress a right angle bend in the tube. However, the clip is bulky and thus can produce an unsightly bump under the patient's skin after implantation. A proximal cannula can also be fashioned from two straight sections of tube joined to the ends of a rigid, right angle, elbow connector. Such cannulae suffer from the drawback that the ligated joint between the end of the tube inserted in the ventricle and the elbow is intradural. When such a shunt system is revised, the intradural tube tends to disconnect from the elbow. Also, revision typically requires dissection of scar tissue growth around the intradural ligature. This often causes undesirable bleeding in the region of the skull hole. According to the present invention, an angled shunt connector has been discovered which includes an extradural nipple for the intradural tube of a proximal cannula.
Therefore, it is an object of the present invention to provide a method for joining medical tubes which is more resistant to unexpected disconnection than connections secured by ligatures.
It is another object of the present invention to provide a medical tube connector for securing a medical tube with uniform consistency. The medical tube connector according to the present invention features an apparatus which can be used to clamp the tube onto a nipple to a preselected tightness. The invention thus provides the advantage that connections made by different physicians can be secured to an effectively identical extent. It is another advantage that the individual manual dexterity of the physician has less influence on the effectiveness of the connection.
It is still another object of the invention to provide a medical tube connector which allows the physician to connect a tube to a nipple when the joint is partially hidden under the skin. Use of the novel medical connector features the ability to secure a tube while reducing the extent of the incision.
It is a further object of the present invention to provide a titanium or titanium alloy medical tube connector for subcutaneous implantation which is radioopaque and which does not interfere with MRI techniques.
It is a still further object of this invention to provide a drain cannula for a VP shunt which provides a low profile, patent, right angle elbow connector which obviates the need for a intradural ligation.
Accordingly, there is now provided an apparatus for draining cerebrospinal fluid from a ventricle of a brain comprising:
(a) a tube connector including PA1 (b) an elastically deformable flexible tube having a distal end, a proximal end opposite the distal end, a lumen emerging from the distal end, and ports at the proximal end for admitting fluid into the lumen; the flexible tube being concentrically mounted on the tube connector to form a fluid tight, lap joint of the distal end of the flexible tube and the second nipple with the elbow bend and intradural arm within the lumen and the first nipple protruding from the lumen at the distal end of the flexible tube, thereby orienting the proximal end at an angle relative to the extradural arm and establishing a fluid passageway through the lumen at the elbow bend.
(1) a rigid, tubular body having a body outer diameter, the tubular body defining a central, longitudinal bore; PA2 (2) an elbow bend in the tubular body defining an intradural arm extending from the elbow bend to one body end and an extradural arm extending from the elbow bend away from the intradural arm defining at least one other body end; PA2 (3) a first nipple near the at least one other body end, at least a portion of the first nipple having a nipple outer diameter larger the body outer diameter; PA2 (4) a second nipple between the elbow bend and the first nipple, at least a portion of the second nipple having a nipple outer diameter larger than the body outer diameter; and